Sunday, February 7, 2016

60 meter transceiver power amplifier

I was able to improve the third order intermodulation. It is now almost 30 db down the wanted signals. It was done by adjusting the bias current for both IRF -510 transistors. I also increased the feedback. That lowers gain but improves linearity.

Below is a picture of the inside of the cabinet. It is getting crowded in there.

I have made an ALC circuit to control the output power. It works but is difficult to align.
That is because the 1350p has 60 db gain controlled by 2-3 volt. Here is some room for improvement.

After this it was time for some on air tests. It was stable during antenna matching.
Then I have used it to dive a external linear amplifier. That works but output power was way too high. We are allowed to use 100W. So I adjusted the power using the ALC to get the 100Watts.
It turns out I needed only 1,5 Watt input to get 100 Watts. So my 5 W amplifier is overkill.
No QSO has been made yet. It is quiet at 60 meters.

Now I am working on the CW unit. Sidetone and semi break in  are working. Now a CW signal must be added to the SSB filter input.
After that the basic functionality is present.



 

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